Seminar

2:00 pm - 3:00 pm

Speaker

Ezekiel Johnston-Halperin
Professor of Physics
The Ohio State University

Bio

Prof. Johnston-Halperin received his B.S. in physics from Case Western Reserve University in 1996, followed in 2003 by his Ph.D. in Physics at the University of California at Santa Barbara in the research group of Prof. David D. Awschalom in the area of semiconductor spintronics. His postdoctoral studies at the California Institute of Technology in the research group of Prof. James R. Heath extended from 2003 to 2006 and covered a number of projects ranging from nanostructured materials and sublithographic patterning to integrating molecular and solid-state materials to form extremely dense electronic circuits. He has been a faculty member in the Department of Physics at The Ohio State University since 2006, and his research program exploits the ability to apply techniques and insights from one subfield of physics in the traditional wheelhouse of another. For example, one current focus is on exploring quantum coherent excitations of organic-based magnets and is informed by his prior work in exploring spin transport and magnetization dynamics in inorganic expitaxial ferromagnet/non-magnetic (FM/NM) heterostructures. In particular, he has been able to demonstrate coherent magnon states that demonstrate the lowest loss of any magnetic thin film developed to date, organic or inorganic. This remarkable discovery is driving much of his current work, as he explores the implications of this unprecedented coherence for applications ranging from non-reciprocal microwave electronics, to topologically protected magnon modes in artificially patterned magnon crystals, to use as a “quantum bus” to transduce between quantum computation and quantum communications in future quantum information systems (QIS). Parallel efforts that are currently at an earlier stage, but with similar long-term focus, include exploring the emergence of electronic topological phases in 2D materials and the use of magnetic functionalization to enable remote actuation and control of nanoscale machines based on DNA origami.

Abstract

The study of quantum coherent magnonic interactions relies implicitly on the ability to excite and exploit long-lived spin-wave excitations in a magnetic material. That requirement has led to the nearly universal reliance on yittrium iron garnet (YIG), which for half a century has reigned as the unchallenged leader in high-Q, low loss magnetic resonance, and more recently in the exploration of coherent quantum coupling between magnonic and spin or superconducting degrees of freedom. Surprisingly, the organic-based ferrimagnet vanadium tetracyanoethylene (V[TCNE]2) has recently emerged as a compelling alternative to YIG. In contrast to other organic-based materials V[TCNE]2 exhibits a Curie temperature of over 600 K with robust room-temperature hysteresis with sharp switching to full saturation. Further, since V[TCNE]2 is grown via chemical vapor deposition (CVD) at 50 C it can be conformally deposited as a thin film on a wide variety of substrates with Q rivaling the very best thin-film YIG devices, which must be grown epitaxially on GGG substrates at temperatures over 800 C. In V[TCNE]2 this Q can be as high as 8,000 (linewidth of 0.50 Oe at 9.86 GHz). Here, we will present evidence of coherent magnonic excitations in V[TCNE]2 thin films and nanostructures, pointing to magnon-magnon coupling that can be tuned into the strong coupling regime and spin-magnon coupling that allows for the transduction of quantum information from 0D to extended quantum states. These results demonstrate the remarkable potential for these structures to play a major role in the emerging field of quantum magnonics, with applications ranging from the creation of highly coherent magnon crystals to quantum sensing and information.